The invention concerns an apparatus for determining an optimum sunscreen factor at any given time for the purpose of selecting a sunscreen preparation suitable for protection of the skin.
During sunbathing, but also under irradiation devices, e.g., sunlamps or the like, many people confront the problem of protecting their skin from the damaging effects of ultraviolet radiation while, on the other hand, still attaining a healthy tanning of the skin in a relatively short period of time.
Many sunscreens exercise over against UV radiation a filtering action. The degree of filtration corresponds to a sunscreen factor, for example, 1-15. These numbers are intended to put the sunscreen user in a position to select a sunscreen with the right factor.
In order to facilitate this selection, one has recently begun announcing on a daily basis as a "sunburn warning", for example, at public beaches on the Adriatic Sea the UV radiation and the corresponding sunscreen factor. Here, one can make good use of a device known as a "Sun-Timer", which, like an exposure meter, collects the UV radiation and converts it electronically into measured values with which the sunscreen factors are coordinated (periodical: HOR ZU, no. 87/1984).
To be sure, this announcement of sunscreen factors, which are also given on the packages of sunscreens, makes things easier for a lot of people. Disadvantageous, however, is the fact that one does not take into consideration the individual state of the skin. This state is usually evaluated on the basis of opinion and superficial inspection.
The parameters to be considered when selecting a proper sunscreen are not only the objective measurement of UV radiation, but also an evaluation of the current state of the skin.
This is basically determined by the skin's subjective, biological nature, for example, light and transparent or brown (pigmented) and opaque and additionally by its state as a result of sunlight or UV radiation. Both factors are responsible for the skin's tanning value at a given point in time. Only the most precise possible determination of this value can provide a reliable basis for the proper selection of the sunscreen factor.
It is also known to use color scales combined with the sunscreen factors, for comparison with the current color of the skin. Thus, a method and device for photocolorimetrically determining the tanning degree of different skin types (German patent No. 20 58 579), which permits photometrically ascertaining the degree of tanning of different human skin types and the establishment of a tanning scale from 0.0% to 100%. This device is designed such that it requires the comparison with one of many color tones (to which a number is assigned in each case) in measuring the degree of tanning of the skin. The device possesses a number of color-tone carriers, either colored plastic cards rotatable around a common axis or sections of a plastic disk. It has been found, however, that these color comparisons can not lead, in practice, to sufficiently reliable selection of the sunscreen necessary in a given case. This is because the color scales do not take into consideration the individual subjective character of a skin.